Nano-titanium dioxide

In a study focusing on nano-titanium dioxide (nano-TiO2) particles found in cosmetics, sunscreens, and other personal care products, Cyndee Gruden, Ph.D. and Olga Mileyeva-Biebesheimer, from the University of Toledo (Ohio), examined the possible impact of nanoparticules on microorganisms.

They studied survival of Escherichia coli (E. coli) bacteria when exposed in laboratory cultures to various amounts of nano-TiO2 and found surprisingly large reductions in survival in samples exposed to small concentrations of the nanoparticles for less than an hour. “How fast the impact was surprised me,” Cyndee Gruden said.

This is a magnification of E. coli exposed to a low concentration (10 mg/L) of titanium dioxide nanoparticles. Cells with compromised membranes are stained red. University of Toledo

The findings open the door to future research, including studies to determine whether the same effects occur in the natural environment.

Indeed, when the particles are washed down the drain in homes as people bathe and end up in municipal sewage treatment plants. From there, they can enter lakes, rivers, and other water But right now, there’s no clear answer regarding the effects that nanoparticles may have on the environment.

Nano-silver, nano-copper oxide and nano zinc oxide

In a second study on nanotoxicity at the ACS National Meeting, Anne Anderson and colleagues at Utah State University and the University of Utah have inserted genes into a strain of Pseudomonas putida (P. putida) - a beneficial soil microbe - so that it emits light upon contact with nanoparticles of heavy metals. The bacteria glow brightly when it is in its normal healthy state. The glow dims upon exposure to toxic substances.

Anderson’s group discovered that P. putida cannot tolerate silver, copper oxide and zinc oxide nanoparticles. Toxicity occurred at levels as low as micrograms per litre. That’s equivalent to two or three drops of water in an Olympic-sized swimming pool. Anderson warns it could spell danger for aquatic life. “If you look up the Environmental Protection Agency’s risk level of Copper to fish and other aquatic organisms, you are at that point of toxicity.”